Acid Mine Drainage
Acid mine drainage (AMD) from abandoned coal mines affects the quality of both groundwater and surface water. Drainage results from various mining methods performed in the watershed. These methods include underground mining, strip mining, and auger mining. The mining process exposes iron sulfide (pyrite) and unremoved coal contained in the sandstone overburden to air and water. These oxidizing conditions result in an increase of acidity, which subsequently decreases the pH and increases the concentrations of dissolved metals. These consequences lead to an overall degradation of water quality and the inability to support aquatic life.
There are two approaches to controlling Acid Mine Drainage. The first is to reduce or eliminate the source of the AMD. One method for source elimination seeks to prevent oxidation by replacing the air within the mine with groundwater. This air-with-water replacement is brought about by sealing any mine openings with an impermeable grouting material. One such material under investigation by ORITE is flue gas desulferization (FGD) material, a by-product from coal-fired power plants. This material is composed of primarily calcium sulfate (gypsum). Another source elimination strategy is to fill the mine with a solid (e.g., FGD or a clay slurry) in order to eliminate the oxidation reaction.
The second primary method for mitigating Acid Mine Drainage involves treating the AMD itself in order to remove the negative impact to the watershed. Chemical, biological, or physical treatments may be used in AMD abatement. Chemical treatments primarily seek to neutralize the acid through the addition of an alkali (e.g., soda ash) with a subsequent sedimentation basin in order to retain metal precipitates after the pH adjustment. Biological treatments use constructed wetlands, as one example, for natural attenuation of biological nutrient additions in order to accelerate indigenous activity. Physical treatment seeks to alleviate the impact through re-routing of streams to circumvent possible problematic geological formations.
Faculty and students in ORITE are studying these and other promising strategies for remediating AMD. For example, compounds found in AMD can be extracted for use in paint and used in artworks, as demonstrated in a collaboration with the John Sabraw of Ohio University’s School of Art + Design. ORITE is currently working to create predictive models—based on water quality, flow rate, and water table measurements taken in the field—to develop groundwater and surface water restoration plans. Further, biological assessments for fish, macroinvertebrates, and algae, along with habitat quality assessments, are utilized to indicate the effectiveness of any implemented abatement strategies. Finally, geographic information systems (GIS) are being developed to assist in the management and dissemination of all the environmental data collected to date.